becketqin commented on a change in pull request #6594: [FLINK-9311] [pubsub] Added PubSub source connector with support for checkpointing (ATLEAST_ONCE) URL: https://github.com/apache/flink/pull/6594#discussion_r300039749
########## File path: flink-connectors/flink-connector-gcp-pubsub/src/main/java/org/apache/flink/streaming/connectors/gcp/pubsub/PubSubSource.java ########## @@ -0,0 +1,298 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.flink.streaming.connectors.gcp.pubsub; + +import org.apache.flink.api.common.functions.RuntimeContext; +import org.apache.flink.api.common.serialization.DeserializationSchema; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.java.typeutils.ResultTypeQueryable; +import org.apache.flink.configuration.Configuration; +import org.apache.flink.runtime.state.CheckpointListener; +import org.apache.flink.streaming.api.checkpoint.ListCheckpointed; +import org.apache.flink.streaming.api.functions.source.ParallelSourceFunction; +import org.apache.flink.streaming.api.functions.source.RichSourceFunction; +import org.apache.flink.streaming.api.operators.StreamingRuntimeContext; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.AcknowledgeIdsForCheckpoint; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.AcknowledgeOnCheckpoint; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.Acknowledger; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.PubSubDeserializationSchema; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.PubSubSubscriber; +import org.apache.flink.streaming.connectors.gcp.pubsub.common.PubSubSubscriberFactory; +import org.apache.flink.util.Preconditions; + +import com.google.auth.Credentials; +import com.google.cloud.pubsub.v1.Subscriber; +import com.google.pubsub.v1.ProjectSubscriptionName; +import com.google.pubsub.v1.PubsubMessage; +import com.google.pubsub.v1.ReceivedMessage; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.io.Serializable; +import java.time.Duration; +import java.util.List; +import java.util.concurrent.CancellationException; + +import static com.google.cloud.pubsub.v1.SubscriptionAdminSettings.defaultCredentialsProviderBuilder; + +/** + * PubSub Source, this Source will consume PubSub messages from a subscription and Acknowledge them on the next checkpoint. + * This ensures every message will get acknowledged at least once. + */ +public class PubSubSource<OUT> extends RichSourceFunction<OUT> + implements Acknowledger<String>, ResultTypeQueryable<OUT>, ParallelSourceFunction<OUT>, CheckpointListener, ListCheckpointed<AcknowledgeIdsForCheckpoint<String>> { + public static final int NO_MAX_MESSAGES_TO_ACKNOWLEDGE_LIMIT = -1; + private static final Logger LOG = LoggerFactory.getLogger(PubSubSource.class); + protected final PubSubDeserializationSchema<OUT> deserializationSchema; + protected final PubSubSubscriberFactory pubSubSubscriberFactory; + protected final Credentials credentials; + protected final int maxMessagesToAcknowledge; + protected final AcknowledgeOnCheckpointFactory acknowledgeOnCheckpointFactory; + + protected transient AcknowledgeOnCheckpoint<String> acknowledgeOnCheckpoint; + protected transient PubSubSubscriber subscriber; + + protected transient volatile boolean isRunning; + + PubSubSource(PubSubDeserializationSchema<OUT> deserializationSchema, + PubSubSubscriberFactory pubSubSubscriberFactory, + Credentials credentials, + int maxMessagesToAcknowledge, + AcknowledgeOnCheckpointFactory acknowledgeOnCheckpointFactory) { + this.deserializationSchema = deserializationSchema; + this.pubSubSubscriberFactory = pubSubSubscriberFactory; + this.credentials = credentials; + this.maxMessagesToAcknowledge = maxMessagesToAcknowledge; + this.acknowledgeOnCheckpointFactory = acknowledgeOnCheckpointFactory; + } + + @Override + public void open(Configuration configuration) throws Exception { + super.open(configuration); + if (hasNoCheckpointingEnabled(getRuntimeContext())) { + throw new IllegalArgumentException("The PubSubSource REQUIRES Checkpointing to be enabled and " + + "the checkpointing frequency must be MUCH lower than the PubSub timeout for it to retry a message."); + } + + getRuntimeContext().getMetricGroup().gauge("PubSubMessagesProcessedNotAcked", this::getOutstandingMessagesToAck); + + createAndSetAcknowledgeOnCheckpoint(); + this.subscriber = pubSubSubscriberFactory.getSubscriber(credentials); + this.isRunning = true; + } + + private boolean hasNoCheckpointingEnabled(RuntimeContext runtimeContext) { + return !(runtimeContext instanceof StreamingRuntimeContext && ((StreamingRuntimeContext) runtimeContext).isCheckpointingEnabled()); + } + + @Override + public void acknowledge(List<String> acknowledgementIds) { + if (!isRunning) { + return; + } + + subscriber.acknowledge(acknowledgementIds); + } + + @Override + public void run(SourceContext<OUT> sourceContext) throws Exception { + while (isRunning) { + try { + blockIfMaxMessagesToAcknowledgeLimitReached(); + + processMessage(sourceContext, subscriber.pull()); + } catch (InterruptedException | CancellationException e) { + isRunning = false; + } + } + subscriber.close(); + } + + void processMessage(SourceContext<OUT> sourceContext, List<ReceivedMessage> messages) throws Exception { + synchronized (sourceContext.getCheckpointLock()) { + for (ReceivedMessage message : messages) { + acknowledgeOnCheckpoint.addAcknowledgeId(message.getAckId()); + + PubsubMessage pubsubMessage = message.getMessage(); + + OUT deserializedMessage = deserializationSchema.deserialize(pubsubMessage); + if (deserializationSchema.isEndOfStream(deserializedMessage)) { + cancel(); + return; + } + + sourceContext.collect(deserializedMessage); + } + + } + } + + private void blockIfMaxMessagesToAcknowledgeLimitReached() throws Exception { + while (maxMessagesToAcknowledge != NO_MAX_MESSAGES_TO_ACKNOWLEDGE_LIMIT && getOutstandingMessagesToAck() > maxMessagesToAcknowledge) { + LOG.debug("Sleeping because there are {} messages waiting to be ack'ed but limit is {}", getOutstandingMessagesToAck(), maxMessagesToAcknowledge); + Thread.sleep(100); + } + } + + private Integer getOutstandingMessagesToAck() { + return acknowledgeOnCheckpoint.numberOfOutstandingAcknowledgements(); + } + + @Override + public void cancel() { + isRunning = false; + } + + @Override + public TypeInformation<OUT> getProducedType() { + return deserializationSchema.getProducedType(); + } + + public static <OUT> PubSubSourceBuilder<OUT> newBuilder(DeserializationSchema<OUT> deserializationSchema, Review comment: These two public methods to get builders are not really a builder pattern. 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